Power transmission mechanism

ABSTRACT

A power transmission mechanism having a reciprocating drive means for imparting rotation to a reversibly rotatable body is improved by having an output drive member connected to the rotatable body and resilient means connecting the rotatable body and the output drive member for transmitting the rotational motion of the rotatable body to the output drive member. The resilient means is deflectable so that it can deflect from its normal position to store a portion of the rotational energy while transmitting the remainder of the rotational energy in the form of rotational movement to the output drive member while the reversibly rotatable body is rotating. The resilient means then reverts to its normal position to release the stored energy and continue moving the output drive member after the reversibly rotatable body is stopped.

IiFSD -MZQ Bradt 1 POWER TRANSMISSION MECHANISM [72] Inventor: Gordon E.Bradt, Wilmette, I11.

[73] Assignee: Bell & Howell Company, Chicago,

Ill.

[22] Filed: Sept. 2, 1969 [21] App]. No.: 854,408

[52] U.S. Cl.. ..74/143, 74/112, 350/187 [51] Int. Cl ..Fl6h 27/02 [58]Field of Search ..74/112, 577, 143, 142, 27; 350/187; 192/55 [56]References Cited UNlTED STATES PATENTS 2,061,827 11/1936 Brooks ..192/55593,313 11/1897 Schultz ..192/55 1,154,891 9/1915 Sharpnack ..192/552,939,561 6/1960 Rudisch ..192/55 2,757,569 8/1956 lsom ..74/1122,995,061 8/1961 Briskin et al ..350/187 3,115,785 12/1963 Simmons..74/142 [4 1 Oct. 17, 1972 Att0rneyFinnegan, Henderson, Farabow &Garrett [57] ABSTRACT A power transmission mechanism having areciprocat-v ing drive means for imparting rotation to a reversiblyrotatable body is improved by having an output drive member connected tothe rotatable body and resilient means connecting the rotatable body andthe output drive member for transmitting the rotational motion of therotatable body to the output drive member. The resilient means isdeflectable so that it can deflect from its normal position to store aportion of the rotational energy while transmitting the remainder of therotational energy in the form of rotational movement to the output drivemember while the reversibly rotatable body is rotating. The resilientmeans then reverts to its normal position to release the stored energyand continue moving the output drive member after the reversiblyrotatable body is stopped.

8 Claims, 8 Drawing Figures PATENTEIJHBT 11 m2 3.688.254

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5 INVENTOI Units of Zoom Lens Travel GORDON BRADT 7 7 zzneya/ jacrsonga/zaow ATTORNEYS POWER TRANSMISSION MECHANISM This invention relates toa power transmission mechanism and more particularly to a mechanism fortransmitting power from a rotating power source.

A great number of power transmission mechanisms which transmit powerfrom a power source are known in the prior art and in recent years thesemechanisms have been developed for use in a zoom lens system such asthose found in motion picture and television cameras. ln an applicationentitled, Power Transmission Mechanism, filed by Henry J. Koeber, U.S.Ser. No. 854, 474 and assigned to the same assignee as the presentinvention, such a power transmission mechanism is described. In thatapplication, the power transmission mechanism includes a reversiblyrotatable body for transmitting power from a rotating power source,reciprocating drive means mounted adjacent the outer periphery of thereversibly rotatable body and movable between an operative position andan inoperative position with respect to the reversibly rotatable bodyand operating means connected to the reciprocating drive means forimparting reciprocative motion to the reciprocating drive means to causethe reciprocating drive means to intermittently engage the rotatablebody and rotate the rotatable body intermittently.

The reversibly rotatable body of that power transmission mechanism canbe connected to a movable lens element or zoom lens of a zoom lenssystem by conventional means such as a key secured to a zoom ring andengaged within a helical groove located on the inner periphery of thereversibly rotatable body. In one embodiment the reversibly rotatablebody has a plurality of ratchet teeth on its outer periphery and isdriven in a reciprocating motion by a reciprocating drive means whichengages the ratchet teeth on the reversibly rotatable body. Thereversibly rotatable body therefore must rotate in an intermittentstepping motion which, although an improvement over the prior artdevices, cannot provide a continuous, rotary motion which is oftendesirable in general, and is particularly desirable when the powertransmission mechanism is to be used for powering a zoom lens system.

Accordingly, this invention advantageously provides a new and improvedpower transmission mechanism that smoothes out the intermittent stepmotion of prior power transmissions that utilize a reciprocating drivemeans. This invention also provides a new and improved powertransmission mechanism that can be used in a zoom lens system to permitthe obtaining of a smooth, uniform, continuous zooming action and asharp image without blur due to the zooming action.

Additional advantages of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of this invention. Theadvantages are realized and attained by means of the instrumentalitiesand combinations particularly pointed out in the appended claims.

The power transmission mechanism with which this invention is usedtransmits power from a rotating power source having a continuous rotarymotion to a reversibly rotatable body having intermitten rotary motion.The mechanism includes reciprocating drive means mounted adjacent theouter periphery of the body, and operating means connected to the drivemeans for imparting reciprocative motion to the drive means to cause thedrive means to intermittently engage and rotate the body. The body hasrotational energy during frictional driving engagement of the body bythe drive means and the body is stopped during frictional drivingdisengagement of the reciprocating drive means.

The present invention as broadly described is the improvement comprisingan output drive member connected to the reversibly rotatable body andresilient means connecting the body and the output drive member fortransmitting the rotational motion of the body to the output drivemember. The resilient means is deflectable from its normal position topermit the resilient means to store a portion of the rotational energywhile transmitting the remainder of the rotational energy in the form ofrotational movement to the output drive member while the body isrotating, and the resiliency of the resilient means being sufficient torevert the resilient means to its normal position to release the storedenergy and continue moving the output drive member after the body isstopped.

Preferably, the output drive member includes an axial groove and theresilient means extends axially into the groove and is frictionallyengaged within the groove to resilient couple the output drive member tothe reversibly rotatable body. Additionally, it is preferred that thegroove have two spaced parallel axially extending walls and theresilient means include two axially extending legs which frictionallyengage the axial extending walls. I

It is also desirable to provide a deflection limiter to limit thedeflection of the resilient means and to provide a non-resilientcoupling when the deflection is so limited. The deflection limiterpreferably extends axially from the reversibly rotatable body and ispositioned within the output drive member in an axial groove havingaxial sides with the deflection limiter being spaced from the axialsides. It is also preferred that the deflection limiter extend into thesame groove as the resilient means, and that the deflection limiterextend between and be spaced from the legs of the resilient means.Alternatively, the output drive member may have a second groove with thedeflection limiter being positioned within the second groove.

The power transmission mechanism can be used to power a zoom lens systemhaving a movable lens element with the output drive member being a zoomring connected to the movable lens element for moving the lens elementaxially when the zoom ring is rotated.

The invention consists in the novel parts, constructions, arrangements,combinations, and improvements shown and described. The accompanyingdrawings, which are incorporated in and constitute a part of thisspecification, illustrate one embodiment of the invention and, togetherwith the description, serve to explain the principles of the invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory but arenot restrictive of the invention.

Of the drawings:

FIG. 1 is a front elevation partially in section of a camera having apower transmission mechanism constructed in accordance with theteachings of this invention;

FIG. 2 is a side elevation partially in section of the camera of FIG. 1with parts omitted for clarity;

FIG. 3 is a sectional view showing the mounting of an actuator lever formoving the reciprocating drive means and the mounting of thereciprocating drive means on the operating means;

FIG. 4 is an enlarged exploded view of the reciprocating drive means andactuator lever;

FIG. 5 is an enlarged view of the reversibly rotatable body and theoutput drive member illustrating the cooperation of the resilient means,the deflection limiter, andthe groove in the output drive member;

FIG. 6 is an enlarged view of a row of ratchet teeth on thereciprocating drive means and illustrating a skip tooth at the end ofthe row of ratchet teeth; and

FIG. 7 is a graph illustrating the relationship between the revolutionsof an eccentric which is an element of the operating means and the zoomlens travel with and without the resilient coupling.

FIG. 8 is a partial side elevation view partially in section showing aresilient mean and a deflection limiter mounted in separate axialgrooves on the output drive member.

With reference particularly to FIGS. 1 and 2, the invention is hereembodied in a camera, designated generally by numeral 10 comprising ahousing, generally 12, on which is mounted a power transmissionmechanism, generally indicated by numeral 14. The power transmissionmechanism is driven by a rotating power source having a continuousrotary motion, such as camera drive motor 58. The power transmissionmechanism powers a zoom lens system which can be coupled to theviewfinder assembly of the camera by conventional means (not shown) sothat the camera operator will always observe in the viewfinder exactlythe same scene which is being photographed at any given point throughoutthe entire range of adjustment of the zoom lens system.

The power transmission mechanism transmits power from the rotating powersource to a reversibly rotatable body having intermittent rotary motion.As here embodied, the reversibly rotatable body is a rotatable wheel,generally 16, connected to a movable lens element 18 by a zoom ring 20for moving the lens element axially when the zoom ring is rotated. Asillustrated in FIGS. 5 and 6, rotatable wheel 16 has a front cylindricalportion 22 which has a row of identical buttressshaped teeth 24, eachtooth having a substantially radially extending face 26 and an inclinedface 28 which extends in a clockwise direction (as viewed from the frontof the camera from the top of the tooth to the body of the rotatablewheel. At the left end of the row of teeth 24 a skip tooth 30 isprovided.

Rotatable wheel 16 also contains a rear cylindrical portion 32 having arow of identical buttress-shaped teeth 34, each tooth having asubstantially radially extending face 36 and an inclined face 38 whichextends from the top of the tooth in a counterclockwise direction to thebody of the rotatable wheel. Buttress teeth 34 thus face in a directionopposite to the direction of buttress teeth 24. At the right end of therow of teeth 34 a gap or skip tooth 30 is provided.

A reciprocating drive means is mounted adjacent the outer periphery ofthe reversibly rotatable body and is movable between an operativeposition and an inoperative position with respect to the reversiblyrotatable body. As here embodied, and as illustrated in FIGS. 3 and 4,the reciprocating drive means is a ratchet pawl 42 which is slidablymounted on an eccentric hub 44 of an eccentric drive gear 46 (FIG. 3)and contains a first radially outwardly extending pawl arm 48 that canbe engaged with buttress teeth 24 on front cylindrical portion 22 and asecond radially extending pawl arm 50 that can be engaged with buttressteeth 34 on rear cylindrical portion 32 (FIG. 4). Pawl arms 48 and 50,respectively, have extensions 52 and 54 so that paw arm 48 can onlyengage buttress teeth 24 and paw] arm 50 can only engage buttress teeth34.

Operating means are connected to the reciprocating drive means forimparting reciprocative motion to the reciprocating drive means to causethe reciprocating drive means to intermittently engage and rotate thereversibly rotatable body. As here embodied, and as shown in FIG. 3, theoperating means include an eccentric drive gear 46 having an eccentricbearing hub 44 which imparts a reciprocative motion to ratchet pawl 42which is slidably mounted on eccentric hub 44. Ratchet pawl 42 therebyintermittently engages rotatable wheel 16 and rotates the wheelintermittently. The rotatable wheel is rotated and has rotational energyduring frictional driving engagement of the wheel by the ratchet pawl 42and the wheel is stopped during frictional driving disengagement ofratchet pawl 42. Gear 46 is driven by pinion gear- 56 which is rotatablydriven by the rotating power source such as camera drive motor 58. Abore 60 passes axially through gear 46 to enable gear 46 to be mountedon and rotate about a shaft 62 mounted on housing 12.

Actuating means are connected to the reciprocating drive means formoving the reciprocating drive means between the operative position andthe inoperative position, and, as here embodied, include an alignmentarm 64 extending radially outwardly from ratchet pawl 42, an actuatorlever 66 having an actuator arm 68 in alignment with the alignment armand resilient means, such as a tension spring 70, for holding actuatorarm 68 and alignment arm 64 in alignment. Spring 70 has two legs 72 and74 positioned on opposed sides 76 and 78 of actuator arm 68 and thecorrespondingly opposed sides 80 and 82 of alignment arm 64. Spring 70is positioned on actuator lever 66 which is mounted on shaft 62forwardly of gear 46. Actuator lever 66 is rotatably mounted on shaft 62and spring 70 is positioned within a recess 84 on actuator lever 66. Ahub 86 is positioned about actuator lever 66 and traps spring 70 withinrecess 84. Actuator lever 66 extends radially outwardly from shaft 62and passes through an opening 87 in a side 88 of housing 12. (FIGS. 1and 3).

Actuator lever 66 is prevented from moving up and down on shaft 62 bythe tight fit of the actuator lever within opening 87 in side 88 ofhousing 12. Actuator lever 66, spring 70, and hub 86 are pivotable aboutshaft 62. A knob 90 is mounted on actuator lever 66 for depressing orraising the lever. A second spring 91 is mounted on camera housing 12and has a pair of legs 94 and 96 positioned on opposite sides ofactuator lever 66 to hold the lever in a centered or inoperativeposition. In this position, the pawl arms of ratchet pawl 42 cannotengage buttress teeth 24 and 34 even if the camera drive motor is inoperation.

In accordance with the invention, an output drive member is connected tothe reversibly rotatable body and resilient means are provided forconnecting the body and the output drive member for transmitting therotational motion of the body to the output drive member, the resilientmeans being deflectable from its normal position to permit the resilientmeans to store a portion of the rotational energy while transmitting theremainder of the rotational energy in the form of rotational movement tothe output drive member while the body is rotating, and the resiliencyof the resilient means being sufficient to revert the resilient means toits normal position to release the stored energy and continue moving theoutput drive member after the body is stopped.

As here embodied, the output drive member is the zoom ring 20 which isconnected to movable lens element 18 for transmitting movement to themovable lens element and the resilient means, generally 92, connectsrotatable wheel 16 and zoom ring 20 for transmitting the rotationalmotion of the rotatable wheel to the zoom ring. Zoom ring 20 has aplanar surface 94 positioned adjacent rotatable wheel 16, and, as shownin FIG. 5, is provided with an axial groove 96 in the planar surface,the groove having two spaced parallel axially extending walls 98 and100. Resilient means 92 is mounted on a planar surface 98 of rotatablewheel 16, and extends axially into groove 96 and is frictionally engagedwithin axial groove 96 to resiliently couple the zoom ring to therotatable wheel. Resilient means 92 comprises a first axially extendingspring leg 102 which has a flange 104 frictionally engaged with axiallyextending wall 98 and a second axially extending spring leg 106 whichhas a flange 108 frictionally engaged with axially extending wall 100.The legs 102 and 106 are joined to each other by a transverse web 110.The resilient means keeps zoom ring 20 continually moving during powertransmission and zoom action even while rotatable wheel 16 is stopped,since it is deflectable from its normal position, shown in FIG. 5, tostore a portion of the rotational energy while transmitting theremainder of the rotational energy in the form of rotational movement tozoom ring 20 while the rotatable wheel is rotating, and the resiliencyof the resilient means is sufficient to revert the resilient means toits normal position to release the stored energy and continue moving thezoom ring after the rotatable wheel is stopped.

Zoom ring 20 has a manually operable control lever 40 which extendsradially outwardly from zoom ring 20 and passes through an opening inhousing 12 so that the control lever can be manually engaged to rotatezoom ring 20 in either a clockwise or counterclockwise direction. (FIGS.1 and 2).

In one embodiment of this invention, a deflection limiter is provided tolimit the deflection of the resilient means and to provide anon-resilient coupling when the deflection is so limited. As hereembodied, this means comprises a deflection limiter 112 which extendsaxially from rotatable wheel 16 and is positioned within zoom ring 20 inan axial groove having axial sides with the deflection limiter beingspaced from the axial sides. As shown in FIG. 5, deflection limiter 112extends into the same groove as the resilient means, that is, groove 96,and the deflection limiter extends between and is spaced from springlegs 102 and 106 of the resilient means.

In an alternative embodiment of the position of the deflection limiterto limit the deflection of the resilient means, and as shown in FIG. 8,the deflection limiter 112 can be positioned within a second axiallyextending groove 114 located on planar surface 94 of zoom ring 20.

In operation, when it is desired to transmit power and obtain a forwardor telescopic adjustment of the zoom lens, knob 90 is depressed whilethe camera motor is running. When knob 90 is depressed actuator lever 66and, therefore, actuator arm 68 are rotated in a clockwise direction.The movement of actuator arm 68 in a clockwise direction flexes spring70 so that spring leg 72 acts on side 76 of alignment arm 64 to rotateratchet pawl 42 in a clockwise direction and thereby press pawl arm 48into contact with buttress teeth 24 on rotatable wheel 16. Becauseratchet pawl 42 is being eccentrically driven by eccentric drive gear46, pawl arm 48 will move back and forth with a reciprocating motion toengage and disengage buttress teeth 24 and, therefore, drive rotatablewheel 16 in a clockwise direction with a pulsing motion. Rotatable wheel16 has a relatively high rotational friction and will rotate with astop-start movement during the operation of the power zoom. Rotatablewheel 16 will rotate during a drive stroke when pawl arm 48 is engagedwith buttress teeth 24 and will stop rotating during a return ordisengagement stroke when pawl arm 48 is disengaged from buttress teeth24. Rotation of rotatable wheel 16 causes spring leg 102 to rotate andresults in the rotation of zoom ring 20 since spring leg 102 transmitsrotational energy to zoom ring 20. However, spring leg 102 does nottransmit all of its rotational energy while rotatable wheel 16 isrotating, but is deflected and stores a por tion of it while rotatablewheel 16 is rotating and during the engagement of pawl arm 48 withbuttress teeth 24. During the disengagement of pawl arm 48 fromrotatable wheel 16, spring leg 102 due to its resilient nature returnsto its original position and thus continues to move zoom ring 20 eventhough rotatable wheel 16 is stationary. This achieves a rate of zoomwhich averages between the intermittent movements of the rotatablewheel, and smoothes the movement of the movable lens so that one sees asmoother lens movement in the viewfinder.

This smoothing effect is graphically illustrated in FIG. 7 whererevolutions of eccentric drive gear 46 are plotted against units of zoomlens travel. The solid line indicates zoom lens travel achieved withoutthe resilient coupling of this invention and the broken line indicateszoom lens travel with the resilient coupling of this invention. It isapparent that without the resilient coupling the motion of the zoom lensapproximates the motion given to the rotatable wheel by the eccentricdrive gear 46; that is, there is no zoom lens motion for the one-halfrevolution where gear 46 is not causing the reciprocating drive means toengage and rotate the rotatable wheel and there is a zoom lens motion inthe form of one-half of a sine function when eccentric drive gear 46causes the reciprocating drive means to engage and rotate the rotatablewheel. The zoom lens thus has an irregular motion with the amplitude ofthe irregular motion being graphically shown in FIG. 7.

When a resilient coupling is added to the zoom mechanism to connect therotatable wheel to the zoom ring, the motion of the zoom lens duringpower zoom action is continuous and although still irregular, theamplitude of the irregular motion is substantially less than theamplitude resulting without the resilient coupling. The zoom lens thusmoves with a rate of movement which averages between the stop-startmovement of the rotatable wheel and thus imparts a smoother, steadiermovement of zoom lens element 18.

The clockwise rotation of the rotatable wheel will continue untilactuator lever 66 is released which causes spring 91 to return actuatorlever 66 to the center or inoperative position and stop the zoom action,or until pawl arm 48 runs out of engagement with the row of teeth 24 andinto skip tooth 30.

When it is desired to transmit power to obtain a reverse or wide angleadjustment of the zoom lens system, knob 90 is raised while the cameramotor is running. When knob 90 is raised, actuator lever 66, andtherefore actuator arm 68, are moved in a counterclockwise direction(when viewed from the front of the camera). The movement of actuator arm68 in a counterclockwise direction flexes spring 70 so that spring leg74 acts on side 82 of alignment arm 64 to rotate ratchet pawl 42 in acounterclockwise direction and thereby press pawl arm 50 into contactwith buttress teeth 34 on rotatable wheel 16. The eccentric drive ofratchet pawl 22 will now move pawl arm 50 with a reciprocating motion onbuttress teeth 34, thus driving rotatable wheel 16 in a counterclockwisedirection with a pulsing motion. The rotation of rotatable wheel 16results in the rotation of zoom ring since spring leg 106 transmitsrotational energy to zoom ring 20. Spring leg 106 acts in a mannersimilar to the action of spring leg 102 described above in that thespring leg is deflected and transmits a portion of the rotational energyimparted to it by rotatable wheel 16 during the rotational movement ofrotatable wheel 16 and stores the remainder of the rotational energy.When rotatable wheel 16 is stopped, spring leg 106 releases its storedenergy by returning to its normal position and continues the movement ofzoom ring 20 even though rotatable wheel 16 is stopped. Therefore, theintermittent motion of zoom lens element 18 exhibited in prior artmechanisms having a reciprocating drive means is transformed into asmoother continuous motion. The zoom action, skip tooth, and actuatorlever then operate in a manner similar to that described above withrespect to the forward movement.

When actuator lever 66 is in an inoperative position, control lever 40can be arcuately moved in either a clockwise or counterclockwisedirection to thereby move zoom ring 20 in a corresponding clockwise orcounterclockwise direction. This movement of zoom ring 20 will result ina corresponding forward or reverse movement of movable lens element 18.Thus, zoom action is always achievable whether the camera motor isrunning or is inoperative. When control lever 40 is moved, zoom ring 20drives rotatable wheel 16. However, when manual control lever 40 isengaged to move zoom ring 20, there is a possibility that the movementof zoom ring 20 will cause an overbending to occur in resilient means92. This overbending can either distort the elastic response of theresilient member of can snap the resilient member off from the rotatablewheel.

However, the provision of deflection limiter 112 prevents overbendingfrom occurring. When zoom ring 20 is manually moved by control lever 40,spring legs 102 and 106 are deflected in either a clockwise orcounterclockwise direction. When a rotational force is applied to zoomring 20 that is great enough to deform or snap the spring legs, thespring legs are deflected and engage the side of deflection limiter 112before they can be overbent or snapped off. The deflection limiter thenabsorbs the excess rotational energy and provides a non-resilientcoupling between the zoom ring and rotatable wheel. Any energy nowtransmitted to zoom ring 20 will manifest itself in the rotation ofrotatable wheel 16 and thus the possibility of overbending the resilientmeans is avoided.

In the embodiment wherein the deflection limiter is positioned within agroove other than the groove in which the resilient means is positioned,the prevention of overbending of the resilient member is similar to thatjust described. In this embodiment, the rotation of zoom ring 20 with aforce great enough to overbend the resilient means will result in zoomring 20 rotating until the walls of the second groove engage deflectionlimiter 112. When zoom ring 20 engages the deflection limiter anon-resilient coupling will be provided and any additional energytransmitted to the zoom ring will result in the rotation of rotatablewheel 16 without any possibility of overbending resilient means 92.

Thus, the invention provides a new and improved power transmissionmechanism that permits the smoothing out of the intermittent motionobtained by prior art mechanisms that utilize a reciprocating drivemeans.

The invention in its broader aspects is not limited to the specificdetails shown and described but departures may be made from such detailswithin the scope of the disclosure without departing from the principlesof the invention and without sacrificing its chief advantages.

WHAT lS CLAIMED IS:

1. In a power transmission mechanism for transmitting power from arotating power source having a continuous rotary motion to a reversiblyrotatable body rotatable in either of two opposite directions, said bodyhaving intermittent rotary motion in either direction and includingreciprocating drive means mounted adjacent the outer periphery of thebody, and operating means driven by the rotating power source andconnected to the drive means for imparting reciprocative motion to thedrive means to cause the drive means to intermittently engage and rotatethe body in one of said two opposite directions, the body havingrotational energy during frictional driving engagement of the body bythe drive means and the body being stopped during frictional drivingdisengagement of the reciprocating drive means, the improvementcomprising: an output drive member connected to the reversibly rotatablebody, and resilient means connecting the body and said output drivemember for transmitting the rotational motion of the body in eitherdirection to the output drive member to drive said drive member in acorresponding direction, said resilient means being deflectable ineither of two opposite directions from its normal position to permitsaid resilient means to store a portion of the rotational energy whiletransmitting the remainder of the rotational energy in the form ofrotational movement in said corresponding direction to the output drivemember while the body is rotating, and the resiliency of said resilientmeans being sufflcient to revert said resilient means to its normalposition to release the stored energy and continue moving the outputdrive member in said corresponding direction after the body is stopped.

2. The power transmission mechanism of claim 1 wherein said output drivemember includes an axial groove and the resilient means comprises adeflectable member that extends axially into the groove and isfrictionally engaged within the groove to resiliently couple the outputdrive member to the reversibly rotatable body.

3. The power transmission mechanism of claim 2 wherein said groove hastwo spaced parallel axially extending walls and said resilient meansincludes two axially extending legs which frictionally engage saidaxially extending walls.

4. The power transmission mechanism of claim 3 including a deflectionlimiter to limit the deflection of said resilient means and to provide anon-resilient coupling when the deflection is so limited.

5. The power transmission mechanism of claim 4 wherein said deflectionlimiter extends axially from said reversibly rotatable body and ispositioned within said output drive member in an axial groove havingaxial sides with said deflection limiter being spaced from said axialsides. I

6. The power transmission mechanism of claim 5 wherein said deflectionlimiter extends into the same groove as the resilient means, and saiddeflection limiter extends between and is spaced from said axially

1. In a power transmission mechanism for transmitting power from arotating power source having a continuous rotary motion to a reversiblyrotatable body rotatable in either of two opposite directions, said bodyhaving intermittent rotary motion in either direction and includingreciprocating drive means mounted adjacent the outer periphery of thebody, and operating means driven by the rotating power source andconnected to the drive means for imparting reciprocative motion to thedrive means to cause the drive means to intermittently engage and rotatethe body in one of said two opposite directions, the body havingrotational energy during frictional driving engagement of the body bythe drive means and the body being stopped during frictional drivingdisengagement of the reciprocating drive means, the improvementcomprising: an output Drive member connected to the reversibly rotatablebody, and resilient means connecting the body and said output drivemember for transmitting the rotational motion of the body in eitherdirection to the output drive member to drive said drive member in acorresponding direction, said resilient means being deflectable ineither of two opposite directions from its normal position to permitsaid resilient means to store a portion of the rotational energy whiletransmitting the remainder of the rotational energy in the form ofrotational movement in said corresponding direction to the output drivemember while the body is rotating, and the resiliency of said resilientmeans being sufficient to revert said resilient means to its normalposition to release the stored energy and continue moving the outputdrive member in said corresponding direction after the body is stopped.2. The power transmission mechanism of claim 1 wherein said output drivemember includes an axial groove and the resilient means comprises adeflectable member that extends axially into the groove and isfrictionally engaged within the groove to resiliently couple the outputdrive member to the reversibly rotatable body.
 3. The power transmissionmechanism of claim 2 wherein said groove has two spaced parallel axiallyextending walls and said resilient means includes two axially extendinglegs which frictionally engage said axially extending walls.
 4. Thepower transmission mechanism of claim 3 including a deflection limiterto limit the deflection of said resilient means and to provide anon-resilient coupling when the deflection is so limited.
 5. The powertransmission mechanism of claim 4 wherein said deflection limiterextends axially from said reversibly rotatable body and is positionedwithin said output drive member in an axial groove having axial sideswith said deflection limiter being spaced from said axial sides.
 6. Thepower transmission mechanism of claim 5 wherein said deflection limiterextends into the same groove as the resilient means, and said deflectionlimiter extends between and is spaced from said axially extending legsof the resilient means.
 7. The power transmission mechanism of claim 5wherein the output drive member has a second groove with the deflectionlimiter being positioned within the second groove.
 8. The powertransmission mechanism of claim 1 wherein the output drive member is azoom ring that is connected to a movable lens element of a zoom lenssystem for moving the lens element axially when the zoom ring isrotated.